Correct, one side to GND, other side to Vout and the middle pin (wiper) to V0. With the variable pot you should be able to turn all pixel on (contrast max) and off. Usually LCDs need a negative voltage for V0 which is provided by Vout. Connecting pin 1 and 3 of the variable pot to 5V and GND will not work, because V0 needs negative voltage below GND.

Oliver

Edit: Not all GLCDs provide negative power at Vout. Best would be to measure the voltage of Vout vs. GND first.